ML21278A144
| ML21278A144 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 09/07/2021 |
| From: | Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML21278A102 | List:
|
| References | |
| NEI 99-04 | |
| Download: ML21278A144 (6) | |
Text
CALVERT CLIFFS UFSAR 5E.1-1 Rev. 47 APPENDIX 5E REDUCTION IN CONTAINMENT PRESTRESS AND LONG-TERM CORRECTIVE 5E.0 ACTIONS FOR VERTICAL TENDON CORROSION 5E.1 REDUCTION IN CONTAINMENT PRESTRESS 5E.1.1 DESIGN BASIS The design basis for the Containment Structure is described in Section 5.1.1.
5E.1.2 DESIGN CRITERIA FOR PRESTRESS In the concept of a post-tensioned Containment Structure, the internal pressure load is balanced by the application of an opposing external force on the structure. Sufficient post-tensioning was applied to the containment cylinder and dome to more than balance the internal pressure. Therefore, a margin of external pressure exists beyond that required to resist the design basis loss-of-coolant accident pressure.
Nominal, bonded reinforcing steel was also provided to distribute strains due to shrinkage and temperature. Additional bonded reinforcing steel was used at penetrations and discontinuities to resist local moments and shears.
The internal pressure loads on the foundation slab are resisted by both the external bearing pressure due to dead load and the strength of the reinforced concrete slab. Thus, post-tensioning was not required to exert an external pressure for this portion of the structure. The post-tensioning system is described in Sections 5.1.2.1, 5.1.4.2, and 5.5.1.
Design load combinations are provided in Sections 5.1.2.2 and 5A.3.1.8.
5E.1.3 DESIGN REANALYSIS As a result of some hoop tendon lift-off values being lower than expected during the third-year tendon surveillance, as required per Reference 1 at the time, a reanalysis of the Containment was performed between 1977 and 1979 to reduce the minimum required prestress. The third year lift-off force values for hoop tendons indicated that there was sufficient post-tensioning to meet design requirements, but that the losses appeared to be more accelerated than originally expected. The results of the reanalysis were used to develop minimum tendon force requirements for continual tendon surveillance.
The basic approach in the reanalysis was to take advantage of conservatism existing in the initial prestressing system and the conventional reinforcing with respect to the allowable stresses provided in Table 5-1. The reanalysis was done to more accurately reflect the expected results of future surveillances without reducing the original intended margins of the design. The strict requirements of the reanalysis were to assure that all the original design criteria was maintained.
The basic approach of the reanalysis was to reduce the prestress on all three major tendon groups by a uniform percentage of 9%. The original containment vertical prestress level of 1.32P would be reduced to 1.2P. Specific load cases, as identified in Sections 5.1.2.2 and 5A.3.1.8 were reanalyzed and those components of the Containment Structure potentially affected by the reduced prestress were reevaluated. The approach was satisfactory for both the hoop and dome tendon groups with all the design criteria satisfactorily met or exceeded. However, the reinforcing steel in the shell/base slab interface was slightly overstressed for the structural integrity test (Containment) working stress design load case. To overcome this localized overstress, the vertical tendon group prestressing level was only reduced to 1.29P. Therefore, all the original design criteria, as outlined in Sections 5.1.2 and 5A.3.1, were completely satisfied, assuring sufficient prestress to be available at the end of the nominal 60-year design life. Those components
CALVERT CLIFFS UFSAR 5E.1-2 Rev. 47 of the Containment Structure not affected by a reduced prestress level were not reevaluated.
Since the only change made in the 1977-1979 reanalysis was to reduce the prestress level, the reanalysis concentrates on the portion of the analysis/design that was affected by prestress. Otherwise, the original analysis calculations and results remain valid.
The 1977-1979 reanalysis was performed in two parts. One part addresses the base/shell haunch issue and used separate models for the base slab, and the haunch that were analyzed manually using classical plate and shell theory and finite difference methods.
Compatibility relationships were used to establish continuity at the slab/shell boundary.
The second part used a finite element analysis (FINEL CE-316) to model the Containment and obtain force and moments as output. Seismic loads were recomputed using a finite element model axisymmetric shells and solids (CE-771), which provided a more exact distribution of seismic loads, compared to those provided in the original seismic analysis.
Results of the analysis were post-processed to convert the force and moments on the concrete and reinforcing steel into stresses.
5E.1.3.1 Summary of Calvert Cliffs Containment Reanalysis The Calvert Cliffs Containment was reanalyzed to check the effect of reduced prestressing forces. The following table illustrates the original design and reanalysis prestressing forces.
Containment Original Prestress Forces Containment Reanalysis Prestress Forces Reduction HOOP 630 K/Ft 573.16 K/Ft 9%
VERTICAL 300 K/Ft 294.2 K/Ft 2%
DOME 360 K/Ft 327.52 K/Ft 9%
The reanalysis consisted of an elastic finite element analysis of the upper containment shell and dome. The lower part of the shell and base slabs were analyzed using cracked section properties in order to incorporate the proper redistribution of stresses. The reanalysis considered applicable dead, thermal, and pressure loadings in addition to the revised prestress forces. The results of the original seismic analysis were used in the reanalysis, as described above. The stresses derived from the reanalysis were checked against the Table 5-1 set of allowables. There is no significant overstressing in either the concrete or the reinforcing steel. The stresses checked include those in the meridional, hoop, and radial directions. The containment stresses from the reanalysis are tabulated in Table 5E-1. The location key, allowable stresses, and general notes are provided in Table 5-1.
5E.
1.4 REFERENCES
- 1.
Nuclear Regulatory Commission Regulatory Guide 1.35, Revision 2, Inservice Inspection of Ungrouted Tendons in Prestressed Concrete Containment Structures
CALVERT CLIFFS UFSAR 5E.1-3 Rev. 47 TABLE 5E-1 STRESS ANALYSIS RESULTS CONTAINMENT STRUCTURE -
SUMMARY
OF CONCRETE AND REINFORCING STEEL STRESSES REINFORCING STEEL COMPUTED (psi)
COMPUTED vs. ALLOWABLE SECTION LOAD CASE m
h
II D+F+L+1.15P C
C III D+F+L+TO+E C
7900 0.26 A-B IV D+F+L+TA+P 10200 9900 0.34 0.33 V
1.05D+F+1.5P+TA 3300 7000 0.06 0.13 VI 1.05D+F+1.25P+TA+1.25E 2900 6900 0.05 0.13 VII D+F+P+TA+E' 2200 7500 0.04 0.14 II D+F+L+1.15P C
C III D+F+L+TO+E 8800 15900 0.29 0.53 C-D IV D+F+L+TA+P 13900 20800 0.46 0.69 V
1.05D+F+1.5P+TA C
21500 0.40 VI 1.05D+F+1.25P+TA+1.25E 8100 21200 0.15 0.39 VII D+F+P+TA+E' 17800 20800 0.33 0.39 II D+F+L+1.15P C
C III D+F+L+TO+E 11200 12000 0.37 0.40 E-F IV D+F+L+TA+P C
5600 0.19 V
1.05D+F+1.5P+TA C
2000 0.04 VI 1.05D+F+1.25P+TA+1.25E C
3100 0.06 VII D+F+P+TA+E' C
5200 0.10 II D+F+L+1.15P C
C III D+F+L+TO+E 14900 12100 0.50 0.40 G-H IV D+F+L+TA+P 27800 22400 0.93 0.75 V
1.05D+F+1.5P+TA 35900 30100 0.66 0.56 VI 1.05D+F+1.25P+TA+1.25E 29200 27800 0.54 0.51 VII D+F+P+TA+E' 24700 24500 0.46 0.45 II D+F+L+1.15P C
C III D+F+L+TO+E 8500 10300 0.28 0.34 J-K IV D+F+L+TA+P 24200 26800 0.81 0.89 V
1.05D+F+1.5P+TA 36400 55600 0.67 1.03 VI 1.05D+F+1.25P+TA+1.25E 31400 36600 0.58 0.68 VII D+F+P+TA+E' 25900 27500 0.48 0.51
CALVERT CLIFFS UFSAR 5E.1-4 Rev. 47 TABLE 5E-1 STRESS ANALYSIS RESULTS CONTAINMENT STRUCTURE -
SUMMARY
OF CONCRETE AND REINFORCING STEEL STRESSES REINFORCING STEEL COMPUTED (psi)
COMPUTED vs. ALLOWABLE SECTION LOAD CASE m
h
II D+F+L+1.15P 9300 C
0.31 III D+F+L+TO+E 15700 27900 0.52 0.93 L-M IV D+F+L+TA+P C
C V
1.05D+F+1.5P+TA 16000 C
0.29 VI 1.05D+F+1.25P+TA+1.25E 400 C
0.01 VII D+F+P+TA+E' C
C II D+F+L+1.15P 20800 25500 0.69 0.85 III D+F+L+TO+E 9500 C
0.32 N-O IV D+F+L+TA+P 18400 24200 0.61 0.81 V
1.05D+F+1.5P+TA 39300 44300 0.73 0.82 VI 1.05D+F+1.25P+TA+1.25E 25900 40500 0.48 0.75 VII D+F+P+TA+E' 20800 32500 0.39 0.60 II D+F+L+1.15P 19800 25600 0.66 0.85 III D+F+L+TO+E 8100 17200 0.27 0.57 P-Q IV D+F+L+TA+P 24400 24300 0.81 0.81 V
1.05D+F+1.5P+TA 37600 41600 0.70 0.77 VI 1.05D+F+1.25P+TA+1.25E 39900 46300 0.74 0.86 VII D+F+P+TA+E' 32900 39200 0.61 0.73
CALVERT CLIFFS UFSAR 5E.1-5 Rev. 47 TABLE 5E-1 STRESS ANALYSIS RESULTS CONTAINMENT STRUCTURE -
SUMMARY
OF CONCRETE AND REINFORCING STEEL STRESSES CONCRETE COMPUTED (psi)
COMPUTED vs. ALLOWABLE SECTION LOAD CASE em eh am ah
II D+F+L+1.15P
-890
-790
-840
-790 12 0.30 0.56 0.03 III D+F+L+TO+E
-2630
-2810
-1520
-1460 24 0.94 1.01 0.07 A-B IV D+F+L+TA+P
-2770
-2670
-930
-880 27 0.92 0.62 0.07 V
1.05D+F+1.5P+TA
-2830
-2590
-640
-540 24 0.63 0.15 0.06 VI 1.05D+F+1.25P+TA+1.25E
-3140
-3140
-780
-730 21 0.70 0.18 0.06 VII D+F+P+TA+E'
-3360
-3470
-930
-880 18 0.77 0.22 0.05 II D+F+L+1.15P
-480
-300
-430
-240 167 0.16 0.29 0.39 III D+F+L+TO+E
-2660
-1480
-840
-310 131 0.89 0.56 0.31 C-D IV D+F+L+TA+P
-2190
-2410
-480
-250 141 0.80 0.32 0.33 V
1.05D+F+1.5P+TA
-2010
-2040
-310
-210 99 0.45 0.07 0.23 VI 1.05D+F+1.25P+TA+1.25E
-2670
-2200
-400
-230 94 0.59 0.09 0.22 VII D+F+P+TA+E'
-3270
-2410
-480
-250 94 0.73 0.11 0.22 II D+F+L+1.15P
-590
-290
-310
-270 116 0.20 0.21 0.39 III D+F+L+TO+E
-1130
-1270
-480
-310 134 0.42 0.32 0.44 E-F IV D+F+L+TA+P
-2110
-2890
-330
-270 128 0.96 0.22 0.42 V
1.05D+F+1.5P+TA
-1870
-2790
-260
-260 88 0.62 0.06 0.30 VI 1.05D+F+1.25P+TA+1.25E
-1810
-2820
-300
-260 97 0.63 0.07 0.32 VII D+F+P+TA+E'
-2110
-2870
-340
-270 98 0.64 0.08 0.32 II D+F+L+1.15P
-160
-260
-130
-240 30 0.09 0.16 0.18 III D+F+L+TO+E
-2170
-1870
-640
-610 123 0.72 0.42 0.74 G-H IV D+F+L+TA+P
-1570
-1940
-240
-300 40 0.65 0.20 0.24 V
1.05D+F+1.5P+TA T
-530
-40
-120 13 0.12 0.03 0.08 VI 1.05D+F+1.25P+TA+1.25E
-630
-930
-140
-170 19 0.21 0.04 0.11 VII D+F+P+TA+E'
-1430
-1540
-240
-250 35 0.34 0.06 0.21 II D+F+L+1.15P
-320
-110
-220
-90 21 0.11 0.15 0.15 III D+F+L+TO+E
-1860
-2390
-710
-1060 40 0.80 0.71 0.29 J-K IV D+F+L+TA+P
-2240
-1140
-330
-210 97 0.75 0.22 0.70 V
1.05D+F+1.5P+TA
-740 T
-140 T
102 0.16 0.03 0.73 VI 1.05D+F+1.25P+TA+1.25E
-1300 T
-210 T
108 0.29 0.05 0.78 VII D+F+P+TA+E'
-1990
-1040
-300
-200 97 0.44 0.07 0.70
CALVERT CLIFFS UFSAR 5E.1-6 Rev. 47 TABLE 5E-1 STRESS ANALYSIS RESULTS CONTAINMENT STRUCTURE -
SUMMARY
OF CONCRETE AND REINFORCING STEEL STRESSES CONCRETE COMPUTED (psi)
COMPUTED vs. ALLOWABLE SECTION LOAD CASE em eh am ah
II D+F+L+1.15P
-1100
-900
-250
-730 129 0.37 0.49 0.47 III D+F+L+TO+E
-2790
-260
-680 T
80 0.93 0.45 0.44 L-M IV D+F+L+TA+P
-800
-2410
-310
-650 144 0.80 0.43 0.45 V
1.05D+F+1.5P+TA
-1000
-3350
-130
-1700 161 0.74 0.40 0.34 VI 1.05D+F+1.25P+TA+1.25E
-20
-3050
-220
-960 258 0.68 0.23 0.54 VII D+F+P+TA+E'
-800
-2600
-310
-810 212 0.58 0.19 0.44 II D+F+L+1.15P T
-540 T
T 72 0.30 (a) 0.46 III D+F+L+TO+E
-480
-20
-180
-150 27 0.27 (a) 0.17 N-O IV D+F+L+TA+P T
-640
-50
-30 113 0.36 (a) 0.72 V
1.05D+F+1.5P+TA
-180
-1440
-50
-20 167 0.40 (a) 0.70 VI 1.05D+F+1.25P+TA+1.25E T
-430
-10 T
170 0.12 (a) 0.72 VII D+F+P+TA+E' T
-780
-40
-20 150 0.22 (a) 0.63 II D+F+L+1.15P
-540
-660 T
T 4
0.37 (a) 0.07 III D+F+L+TO+E
-590
-990
-270
-100 47 0.55 (a) 0.83 P-Q IV D+F+L+TA+P
-950
-980
-170 T
17 0.54 (a) 0.30 V
1.05D+F+1.5P+TA
-1850
-1810
-170 T
11 0.51 (a) 0.13 VI 1.05D+F+1.25P+TA+1.25E
-850
-1540
-110 T
48 0.43 (a) 0.56 VII D+F+P+TA+E'
-980
-1840
-130 T
58 0.51 (a) 0.68 (a) fa = 0.3